EP0287777B1 - Clamping device for tools or work pieces having a cylindrical shaft - Google Patents

Abstract

A coupling device for coupling, for example a shaft of a tool, to a coupling member anchored to a machine tool, comprises a take-up bushing formed with a conical recess receiving a substantially conical tapered sleeve which receives the shaft and is formed by at least two portions lying at two opposite sides relative to a central axis of the tapered sleeve. The sleeve is pressed into the bushing to retain the shaft in the coupling device.

Description

The invention relates to a device for holding a tool or workpiece having a shank according to the preamble of patent claim 1.

Such a device is known from DE-AS 24 25 800. This device is used to hold an electrode of a spark erosion machine. There the other part or coupling part, which is firmly connected to the spark erosion machine, has a conical opening into which a conical shaft of the coupling part to be held is inserted. The taper of the shaft and coupling part must correspond to one another as exactly as possible. Furthermore, the coupling part has a transverse opening through which a cross-member defining a coupling surface is guided, which in turn has a central, square opening. The cone-shaped shaft has an axial projection with a radial widening, which can be pushed through the square opening of the crossbar and locks the shaft to the crossbar after rotation of the shaft by 90 degrees.
The coupling part also has an external thread which interacts with an internal thread of a union nut. The union nut presses elastic washers against the crossbar with one shoulder and thus pulls the cone of the shaft into the conical opening of the coupling part, whereby due to the elasticity of the washers, the contact pressure acting on the cone is decoupled to a certain extent from the tightening torque of the union nut. In addition, another ring is attached to the opening of the union nut, which comes to rest against a stop shoulder of the coupling part, as a result of which the union nut can only be screwed in up to this stop. When the union nut is loosened, the last-mentioned ring acts against the crossmember and thus drives the conical shaft out of the conical opening.

This known device is not suitable as a receptacle for parts with a different cross-sectional shape. In particular, this device cannot be used to establish a connection to a cylindrical shaft.

DE 33 04 990 A1 describes a clamping device for spindles of machine tools, which has a radially clamping clamping cylinder which is arranged in a cone receptacle of the spindle and is held by means of a union nut. The conical part is unslotted and rigid and has a hydraulically deformable expansion sleeve in its interior. The union nut is rotatable, but axially immovable, supported between the spindle thread and the engagement part for the hydraulic tensioning of the expansion sleeve. The actual clamping of a workpiece or a tool takes place solely through the expansion sleeve. This known clamping device is ultimately composed of two clamping devices, namely, on the one hand, from the cone holder and the cone part, which is clamped in the cone holder, and on the other hand, from the expansion sleeve, with which a tool or a workpiece is clamped.

The reference Weck, M .: "Machine Tools", Volume 1, VDI-Verlags GmbH, Dusseldorf 1980, pp. 304, 305 describes a chuck with a conical receiving opening into which a conical collet insert is used. The collet insert consists of several steel disks which are elastically connected to each other by rubber intermediate layers, so that the collet insert as a whole only forms a single body. The collet insert is pulled into the cone by a clamping drive, which means that cylindrical shafts or rod material can also be clamped. The collet insert is secured against falling out by a union nut. The purpose of this device is primarily the mass production of bar materials on single and multi-spindle machines, where the use of a complex and expensive clamping device can be justified.

In another known fastening system, cylindrical shanks can be used as tool holders or workpiece holders. Here, a lowering electrode for spark erosion, which is initially to be machined as a workpiece itself and is to be used as a tool after completion of shaping, is soldered to an end face of a cylindrical shaft. Then the cylindrical shaft is inserted into a chuck and after determining its position in relation to the end face of the chuck both in terms of height and circumferential direction by means of two pins, one of which protrudes from the cylindrical shaft against the end face of the chuck and at the same time against another pin protruding axially from the end face, clamped. Together with the soldered-on shaft as a handling aid, the prospective lowering electrode runs through all the necessary processing steps. On completion of the same shaft, it is also used as a sinking electrode on a sinker EDM machine.

The disadvantage of this solution is the complex soldering of the workpiece or tool to the cylindrical shaft. In addition, soldering is not possible with all materials. The round shank penetrating the chuck also limits the possible combinations when coupling to the EDM machine. With larger shank diameters, the parts made of shank and tool or workpiece become voluminous, heavy and expensive, and their storage for later reworking is also made more difficult.

Starting from the device mentioned at the outset, the object of the present invention is to further develop this device in such a way that it is also suitable for receiving shafts which have a non-conical shape.

This object is achieved in a device of the type mentioned in the preamble of claim 1 by the features specified in the characterizing part of patent claim 1.

With the device according to the invention, which is designed in particular as an integral part of a coupling part, improved stability is achieved because of the more favorable ratio of the coupling surface as the base surface to the free shaft length compared to the known fastening system. This also makes it possible to carry out machining operations on the held workpieces or by means of the held tool, in which large forces occur, e.g. when filming.

In these machining steps, which take place with a strong force, heating of the tool or workpiece also occurs, which, in the absence of a soldered connection, cannot result in detachment from the shaft in the invention.

The combination of the device according to the invention with the coupling described above also creates the possibility of indexing the object held on the shaft, ie a precise, predetermined orientation between the shaft and coupling part with respect to a rotation about the longitudinal axis of the shaft in different rotational positions. Of course, a reference marking can also be attached here.

The split insert bushings, which allow the pressing and holding of shafts of different diameters in the slightly conically narrowing recess of the receiving sleeves in the manner of a self-locking Morse cone, can be achieved by die-casting a metallic one Material, preferably aluminum or by injection molding a suitable plastic quickly and without the need for post-processing as cheap disposable parts. With the aid of the device according to the invention, automated handling of the holding shafts together with the objects fastened therein is also possible.

The invention is explained in more detail, for example, using a preferred embodiment according to the drawing.

Fig. 1

einen Axialschnitt durch eine Vorrichtung gemäß der Erfindung in der Schnittebene I-I gemäß der Fig. 2 im Aufriß;

Fig. 2

die Ansicht der Vorrichtung gemäß der Fig. 1 von unten, wobei in der konischen Ausnehmung der Aufnahmehülse eine zweiteilige Einsatzbuchse mit kreiszylindrischem Innenraum eingesetzt ist;

Fig. 3

die gleiche Ansicht wie in der Fig. 2, wobei jedoch der Innenraum der zweiteiligen Einsatzbuchse einen Viereckquerschnitt aufweist;

Fig. 4

einen Axialschnitt durch die Vorrichtung nach der Erfindung, bei der ein Werkstück an einem Schaft fixiert ist;

Fig. 5

einen Axialschnitt der Vorrichtung nach der Erfindung, zur Darstellung der Befestigung zweier schaftartiger Teile aneinander.

Fig. 6

einen Axialschnitt der Vorrichtung nach der Erfindung nach einer weiteren Variante der Erfindung;

Fig. 7

eine Ansicht der Vorrichtung gemäß Fig. 6 von unten, wobei der Schaft rechteckig ist und die zweiteilige Einsatzbuchse keilförmig ist;

Fig. 8

eine Ansicht ähnlich Fig. 7 jedoch mit vierteilige Einsatzbuchse bei rechteckiger konischer Öffnung;

Fig. 9

eine Ansicht ähnlich Fig. 7 mit rechteckigem Schaft zweigeteilter Einsatzbuchse bei einer kreisförmigen, konischen Bohrung.

Show it :

Fig. 1

an axial section through a device according to the invention in the sectional plane II of FIG 2 in elevation.

Fig. 2

the view of the device of Figure 1 from below, wherein a two-part insert bushing with a circular cylindrical interior is used in the conical recess of the receiving sleeve.

Fig. 3

the same view as in Figure 2, however, the interior of the two-part insert bush has a square cross-section.

Fig. 4

an axial section through the device according to the invention, in which a workpiece is fixed to a shaft;

Fig. 5

an axial section of the device according to the invention, to illustrate the attachment of two shaft-like parts to each other.

Fig. 6

an axial section of the device according to the invention according to a further variant of the invention;

Fig. 7

a view of the device of Figure 6 from below, the shaft is rectangular and the two-part insert bushing is wedge-shaped.

Fig. 8

a view similar to Figure 7 but with four-part insert bushing with a rectangular conical opening.

Fig. 9

a view similar to FIG. 7 with a rectangular shaft two-part insert bush with a circular, conical bore.

In the upper part of Fig. 1, the above-mentioned clutch is shown schematically according to an unpublished prior art. Coupling part 1, indicated by dash-dotted lines in the upper position, is firmly anchored to a die-sinking EDM machine, not shown. It has limited elastically deformable transmission elements 1.1, each of which is engaged by a rigid profile piece in the form of a cylinder pin 2.1 provided on the coupling part 2 drawn with solid lines in the lower position. A relative movement of the two coupling parts 1, 2 in the main directions x, y, z of the space is prevented, as is described in more detail in said patent application.

On the side facing away from its coupling surface 2.2 of the lower coupling part 2, which can be freely handled in the decoupled state, a receiving sleeve 2.3 is formed with a bore 2.4 open towards its free end, which narrows slightly conically in the direction of the coupling surface 2.2. In the bottom of the receiving sleeve 2.3 facing the coupling surface 2.2 and coaxially to the conical bore 2.4 there is a threaded bore 2.5. Following the latter, a larger cylinder bore 2.6 is visible in FIG. 1. While the larger cylinder bore 2.6 serves to receive a device which is known per se and which braces the two coupling parts 1, 2, the threaded bore 2.5 is provided for an auxiliary tool to be explained further below. Clamping device and auxiliary tools are the better For clarity not shown in FIG. 1.

An insert sleeve 3 composed of two halves 3.1 is pressed into the conically narrowing bore 2.4 of the receiving sleeve 2.3. These halves are designed such that they together form an outer surface with a taper corresponding to that of the bore 2.4, while the interior of the insert bush 3 is cylindrical and open at both ends. The likewise cylindrical shaft 4.1 of a lowering electrode 4 is clamped in this interior. The two halves 3.1 of the insert bushing 3 have radially projecting ribs 3.2 which run in the axial direction on the conical outside. To ensure the positional symmetry of the halves 3.1 of the insert bush 3 around the shaft 4.1, the ribs 3.2 each engage in a groove 2.7 machined into the wall of the conical bore 2.4 (cf. FIGS. 2 and 3).

With these two ribs, indexing by 180 degrees is possible. Instead of two ribs, three, four or more ribs can also be provided, with which one then indexes around
120 degrees, 90 degrees etc.

The interacting conical surfaces of the insert bushing 3 and the bore 2.4 in the receiving sleeve 2.3, with the aid of the divided insert bushing 3, which works according to the type of collet, hold the shaft 4.1 of the lowering electrode 4 in a manner similar to a self-locking Morse cone. The representation in FIGS. 1 to 3 with a gap between the cut lines of said ones, which are tightly pressed against one another in terms of reality, was chosen for the sake of clarity.

A circular opening 3.3 is formed coaxially with the cylindrical interior of the insert sleeve 3 in the bottom of the insert sleeve 3, which comes into contact with the end face of a shaft 4.1 when it is placed on the end of each. The diameter of the circular opening 3.3 is smaller than that of the interior. Through the circular opening 3.3, an auxiliary tool which can be screwed into the threaded bore 2.5 in the bottom of the receiving sleeve 2.3 facing the coupling surface 2.2 can pry against its adjacent end surface for removing a held shaft 4.1.

While the receiving sleeve 2.3 is expediently produced by die casting a metal, preferably aluminum, in one piece with the lower coupling part 2, the insert bushing can advantageously also be produced either by die casting a metallic material, preferably again aluminum, or by injection molding a plastic. This allows a quick and precise production of the parts of the insert bush 3 with relatively little effort as cheap disposable parts that do not require any reworking.

The choice of insert bushings 3 with different inner diameters enables electrodes or other tools and workpieces to be held regardless of the diameter of their cylindrical shafts.

The parts of the holding device according to FIG. 3 are identical to those in FIGS. 1 and 2 with the same reference numbers, apart from the square shaft 4. 1ʹ and the correspondingly shaped interior of the insert bushing 3ʹ, which is composed of the halves 3.1ʹ.

Fig. 4 shows the attachment of a workpiece WS on a Shank 5. The workpiece here has a conical blind hole 2.4, which tapers from the outside to the inside. The bottom of the blind hole serves as the stop surface 2.2. The connection in turn takes place via an insert socket consisting of two halves 3.1, which likewise has the circular opening 3.3 on its bottom. To separate workpiece WS and shaft 5, a bolt can be screwed through the shaft 5 into a threaded bore (not shown), which applies the axial force required for the separation.

Fig. 5 shows that the device according to the invention can also be used to connect two shafts 6 and 7. One shaft 7 has a larger diameter than the other shaft 6 and also has a conical blind hole 2.4, the flat bottom of which is designed as a stop surface 2.2. The connection here also takes place via an insert bushing formed from two halves 3.1 according to the other exemplary embodiments of the invention. Here, however, the socket is designed without a bottom, so that the front end of the shaft 6 comes to rest directly on the stop surface 2.2 of the other shaft 7.

Fig. 6 shows an axial section of the device according to the invention similar to Fig. 1, but in contrast to the embodiment of Fig. 1, however, the coupling part 2 as the receiving sleeve (2.3) has only two mutually opposite webs 2.3, the mutually facing walls run at an acute angle to each other, i.e. form a cone. The edge portions of these webs are - as shown in FIG. 7 - limited by stops 2.8 running perpendicular to the webs 2.3. Two wedges 3.1 are used as insert bushing 3, their outward-facing surface of the slope or the The cone of the webs 2.3 and their inwardly facing surface is adapted to the shape of the shaft 4.1. In the embodiment of FIGS. 6 and 7, the shaft 4.1 is rectangular. The parts of the wedges 3.1 lying in the region of the end of the shaft 4.1 have two stops 3.4 which are directed inwards, ie towards the other wedge, at which the end face of the shaft 4.1 comes to a stop.

FIG. 7 shows a plan view from below of the device of FIG. 6, FIG. 6 again showing a section along the line II-II of FIG. 7.

In a further embodiment of the invention shown in FIG. 8, both the shaft 4.1 and the recess 2.4 each have a square cross section. The respectively opposite side walls of the recess are inclined at an acute angle to one another, which again results in the taper. The insert bushing here consists of four wedges 3.1, which can otherwise be designed in the same way as the wedges of FIGS. 6 and 7.

FIG. 9 shows a further variant of the invention, in which - similarly to FIGS. 1 and 2 - the conical recess 2.4 has a circular cross section and the shaft 4.1 again has a rectangular cross section. The insert bushing consists of two truncated cone segments, so that in the axial direction the curved outer surface has a slight taper, while the cut surface pointing towards the shaft 4.1 is axially parallel. The cross section of the halves 3.1 of the insert bush is therefore a circular section (circle segment). Here too, as in FIG. 2, there are two grooves 2.7 lying opposite one another in the receiving sleeve 2.3 and ribs 3.2 projecting on the outside of the halves 3.1 of the insert bushing provided for centering, guidance and alignment.

Claims (12)

1. Apparatus for mounting a tool or workpiece, having a shaft (4.1), on a coupling part (2), comprising a coupling surface (2.2), of a coupling whereof the other coupling part (1) is anchored to a machine tool, the coupling surface (2.2) of the one coupling part (2) facing the other coupling part (1) when the coupling parts (1, 2) are connected to one another and one of the coupling parts (2) comprising a cutout (2.4) which tapers comically in the direction from its opening towards the coupling surface (2.2), characterized in that there can be introduced into the comical cutout (2.4) a divided insertion bush (3.1) whereof the outer surface tapers in a manner corresponding to the conical cutout (2.4) and which for receiving the shaft (4.1; 5) has an interior which is matched to the external contour of said shaft (4.1; 5), in that the insertion bush (3) has a floor (3.4) with which the end of a shaft (4.1; 5), inserted into the interior, of the tool or workpiece can be brought into bearing engagement, it being possible to press the insertion bush together with the shaft (4.1), inserted into the interior of said insertion bush, of the tool or the workpiece into the cutout (2.4).
2. Apparatus according to Claim 1, characterized in that the cutout (2.4) is provided in a receiving sleeve (2.3) of the - coupling part (2) anchored to the machine, at the side remote from the coupling surface (2.2) of the coupling part (2), and in that the divided insertion bush (3.1) has a cylindrical interior which is open at both its ends and into which the end to be clamped of the shaft (4.1) of the respective tool or workpiece cam be inserted and together with it cam be pressed with the insertion bush (3) into the cutout (2.4).
3. Apparatus according to Claim 2, characterized in that there is provided in the floor of the insertion bush (3) a central circular opening (3.3) whereof the diameter is smaller than that of the cylindrical interior of the insertion bush (3).
4. Apparatus according to one of Claims 1 to 3, characterized in that the insertion bush (3) is divided by an axial cut into two halves (3.1).
5. Apparatus according to one of Claims 1 and 4, characterized in that there are provided on the outer, comical surface of the insertion bush (3) radially projecting ribs (3.2) which engage in associated grooves in the comical cutout (2.4).
6. Apparatus according to one of Claims 1, 2, 4 and 5, characterized in that the interior of the insertion bush (3) has a polygonal area of cross-section.
7. Apparatus according to one of Claims 1 to 6, characterized in that there is made in the floor of the receiving sleeve (2.3) facing the coupling surface (2.2) and coaxially with respect to the comical cutout (2.4) of said receiving sleeve (2.3) a threaded bore (2.5) whereof the diameter is smaller than that of the central circular opening (3.3) in the floor of the insertion bush (3).
8. Apparatus according to Claims 6 and 7, characterized in that the threaded bore (2.5) has in the floor of the receiving sleeve (2.3) facing the coupling surface (2.2) an area of cross-section which is smaller than the area of polygonal cross-section of the interior of the insertion bush.
9. Apparatus according to one of Claims 1 to 8, characterized in that the insertion bush (3) is composed of at least two metal die-castings (3.1) or plastics injection mouldings which each have the shape of part of a cone.
10. Apparatus according to Claim 1, characterized in that the comical cutout (2.4) of the coupling part (2) is formed by two mutually opposing flat walls (2.3) of the coupling part (2) which run at an acute angle with respect to one another, and in that the insertion bush (3) comprises two wedges (3.1) (Figs. 6 and 7).
11. Apparatus according to Claim 6, characterized in that the conical opening (2.4) has a four-sided cross-section, and in that the insertion bush (3) comprises four wedges (3.1).
12. Apparatus according to Claim 1, characterized in that the conical opening (2.4) has a circular cross-section, in that the shaft (4.1) has a rectangular cross-section, and in that the individual parts (3.1) of the divided insertion bush (3) in cross-section have the shape of a circle segment.

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